Base for an office chair



FIG. 1 is a perspective view of a base for an office chair incorporating the design of the present invention;

FIG. 2 is a top plan view of the base for an office chair;

FIG. 3 is a bottom plan view of the base for an office chair; and,

FIG. 4 is a side elevational view of the base for an office chair. 

The ornamental design for a base for an office chair, as shown and described. 